(1) Field of the Invention
The present invention relates to a thin film transistor (“TFT”) array panel, a display device including the same, and a manufacturing method thereof.
(2) Description of the Related Art
A liquid crystal display is one of the most widely used flat panel displays. The liquid crystal display is a display device that includes two display panels on which electrodes are formed, and a liquid crystal layer that is disposed therebetween, and controls the intensity of transmitted light by rearranging liquid crystal molecules of the liquid crystal layer by applying the voltage to the electrodes.
A TFT array panel that is one of two display panels constituting the liquid crystal display, is used as a circuit board for independently driving each pixel in a liquid crystal display, an organic electro luminescence (“EL”) display device, and the like.
In general, the TFT array panel includes a scanning signal wire or gate wire that transmits a scanning signal, an image signal line or data wire that transmits an image signal, a TFT that is connected to the gate wire and the data wire, a pixel electrode that is connected to the TFT, a gate insulating layer that covers and insulates the gate wire, and an interlayer insulating layer that covers and insulates the TFT and the data wire.
The TFT array panel including a plurality of layers may be manufactured by a pattern of each layer being formed using a photosensitive thin film, through exposure and development processes using a photomask for each layer, and etching the thin film with the mask. However, since a large cost is required when a photomask is used, as the number of masks is decreased, the manufacturing cost is decreased.
In a case when the semiconductor that is included in the TFT uses oxide semiconductor, the characteristic of the semiconductor is excellent but the oxide semiconductor may be easily damaged in a manufacturing step.
In the case when a bottom gate of the TFT is formed using the oxide semiconductor, when the oxide semiconductor is exposed to the atmosphere, or when the metal that is formed on the oxide semiconductor is dry etched, a channel part is damaged by steam (H2O) in the atmosphere or by dry etching gas, such that the characteristic of the TFT may be seriously degraded. In addition, a wet etching method may be considered in order to remove the damage by the dry etching as described above. However, in the case when an etching speed of the oxide semiconductor is faster than an etching speed of the upper metal, it is impossible to form the TFT.
Therefore, after the oxide semiconductor layer is formed, the oxide semiconductor may be damaged by the etching solution that is used when the source electrode and drain electrode are formed thereon. In order to reduce the damage, in general, an etching prevention layer is formed on the oxide semiconductor layer. However, in the case when the etching prevention layer is further formed, since a mask for forming the etching prevention layer is further required, the manufacturing cost is increased and the manufacturing steps become complicated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.